X0305 4 2012-04-26 0001520262 Alkermes plc. ALKS 0001236440 BLOOM FLOYD E CONNAUGHT HOUSE 1 BURLINGTON ROAD DUBLIN 4 IRELAND 1 Common Stock 2012-04-26 4 P 0 20000 17.5914 A 90281 D Common Stock 9028 I Floyd E Bloom Charitable Remainder Trust Common Stock 21066 I Jody Corey-Bloom Charitable Remainder Trust The reporting person's purchase of Alkermes plc ordinary shares reported herein was made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person and was inadvertently effected one day prior to the expiry of the six-month holding period mandated under Section 16(b) of the Securities Exchange Act of 1934. This purchase is matchable to the reporting person's sale of the same number of shares on October 28, 2011. The reporting person and Alkermes plc have entered into an agreement under which the reporting person has paid Alkermes plc the full amount of the profit realized in connection with the short-swing transaction, less transaction costs. The price reported in Column 4 is a weighted average price. The shares were purchased in multiple transactions at prices ranging from $17.47 to $17.93. Full information regarding the number of shares purchased at each separate price can be furnished to the SEC staff upon request. /s/ Jennifer Baptiste, attorney-in-fact for Floyd Bloom 2012-04-27